Messages in this thread Patch in this message | | | From | Aubrey Li <> | Subject | [PATCH v4 2/2] proc: add AVX-512 usage to /proc/pid/status | Date | Tue, 11 Dec 2018 08:24:48 +0800 |
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AVX-512 components usage could cause core turbo frequency drop. So it's useful to expose AVX-512 components usage as a heuristic hint for the user space job scheduler to cluster the AVX-512 using tasks together.
Example: $ cat /proc/pid/status | grep AVX512_hint AVX512_hint: 1
The hint number '0' indicates the task recently didn't use AVX-512 components thus unlikely has frequency drop issue. And the number '1' indicates the task recently used AVX-512 components thus could cause core frequency drop. User space tools may want to further check by:
$ perf stat --pid <pid> -e core_power.lvl2_turbo_license -- sleep 1
Performance counter stats for process id '3558':
3,251,565,961 core_power.lvl2_turbo_license
1.004031387 seconds time elapsed
Non-zero counter value confirms that the task causes frequency drop.
Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> --- arch/x86/kernel/fpu/xstate.c | 19 +++++++++++++++++++ fs/proc/array.c | 5 +++++ 2 files changed, 24 insertions(+)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 87a57b7642d3..98baa47c97b0 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -7,6 +7,7 @@ #include <linux/cpu.h> #include <linux/mman.h> #include <linux/pkeys.h> +#include <linux/seq_file.h> #include <asm/fpu/api.h> #include <asm/fpu/internal.h> @@ -1245,3 +1246,21 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf) return 0; } + +/* + * Report CPU specific thread state + */ +void arch_task_state(struct seq_file *m, struct task_struct *task) +{ + /* + * Check the processor and build option if AVX512 is supported. + */ + if (!cpu_feature_enabled(X86_FEATURE_AVX512F)) + return; + /* + * Report AVX-512 components usage: + */ + seq_put_decimal_ull(m, "AVX512_hint:\t", + task->thread.fpu.avx512_usage ? 1 : 0); + seq_putc(m, '\n'); +} diff --git a/fs/proc/array.c b/fs/proc/array.c index 0ceb3b6b37e7..dd88c2219f08 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -392,6 +392,10 @@ static inline void task_core_dumping(struct seq_file *m, struct mm_struct *mm) seq_putc(m, '\n'); } +void __weak arch_task_state(struct seq_file *m, struct task_struct *task) +{ +} + int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) { @@ -414,6 +418,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, task_cpus_allowed(m, task); cpuset_task_status_allowed(m, task); task_context_switch_counts(m, task); + arch_task_state(m, task); return 0; } -- 2.17.1
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